Liu Zi Jue (the art of expiration by producing six different sounds) is a traditional exercise that promotes health. It is practiced through the art of expiration. It has a long history and is quite widespread. The earliest record for this type of Qigong dates back to the Southern and Northern Dynasties (420 - 589 AD). During the process of its spread, the masters of medicine and regimens over various generations replenished and improved it. The current adaptation is based upon the traditional one, but utilizes modern scientific theories and methods. The order of the six characters, the pronunciation and the degree of lip-rounding have been regulated and standardized to make it more scientific and reasonable.
(China.org.cn February 14, 2008)